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Jonathan Harris

ADC Noise: The Clock Input & Phase Noise, Part 3 – Test Setup

Jonathan Harris
jonharris0
jonharris0
4/29/2014 8:02:29 PM
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Re: Two PCB –Phase/Clock Noise
Hi DaeJ, the AD9523 phase noise will defintely be affected by the jitter of its reference source.  The point here in this blog was not to evaluate the AD9523 jitter performance but rather to look at the effect of the output jitter (phase noise) on the SNR of the AD9643.  Also, you have a very good point with the PCB.  It is always important to consider good design practices when designing PCBs such that additional noise from other sources on the PCB do not impact the noise in the ADC.  I'd recommend looking back over some of my blogs related to ADC noise for some nuggets along those lines.  Thanks for the great comments!

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DaeJ
DaeJ
4/19/2014 6:50:52 PM
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Two PCB –Phase/Clock Noise
Firstly, it would be better to review other components with AD9523 in order to understand how SNR is affected in the test setup. Secondly, engineer might investigate Phase and Clock noise in different layer design of PCB board. For example, figure 2 shows that the number of input source is feeding into one of PCB, influencing the noise naturally.

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More Blogs from Jonathan Harris
We will continue looking at the AD9680 as an example just as we did in part 1. Similar to the real mode operation of the DDC the normalized decimation filter responses are the same regardless of speed grade.
Let’s now take a closer look at the decimation filtering and how ADC aliasing influences the effective response of the decimation filtering
Increase the decimation ratio in the DDC to see the effects of frequency folding and translating when a higher decimation rate is employed along with frequency tuning with the NCO.
Let’s now take a look at a real example with the AD9680-500. We’ll see how this simple yet powerful tool can be used to aid in understanding the aliasing effects of an ADC as well as help with understanding effects of some digital processing blocks in the AD9680.
Back in my April blog post this year, we took some time to look at the Frequency Folding Tool that is available on the Analog Devices web site. I would like to revisit this tool as there have been a few handy improvements that have been made based on some great feedback.
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